Urgent remedial work must be carried out to save Silbury Hill from collapse, English Heritage said yesterday. The threat to the 130ft mound, which is one of the West's most mysterious prehistoric monuments, was blamed on excavations made for a BBC TV documentary in the 1960s, presented by former Mastermind presenter Magnus Magnusson.

An English Heritage survey has revealed that the late Professor Richard Atkinson's tunnel, which was dug in 1968/69 was not, as previously thought, properly filled in.

The unexpected discovery is already causing minor internal collapses and 'voids' within Europe's largest man-made hill that will, in time, reach the surface. If unattended, it will damage highly significant deposits in the centre of the structure that contain its early history and perfectly preserved plant and animal remains.

English Heritage says it is considering three options:

Pumping chalk slurry into the voids.

Re-opening the tunnel and backfilling by hand.

As above, but supporting the tunnel to allow repeated access.

Respected West archaeologist Mike Pitts, editor of British Archaeology magazine which revealed the threat, urged English Heritage to act swiftly.

Source: Western Daily Post 4 February 2005